Thread severing



April 30, 1963 c. F.1F1TZGERALD ETAL 3,087,448

THREAD SEVERING 2 Sheets-Sheet 1 Original Filed Feb. 8, 1957 April 30, 1963 c. F. FITZGERALD ET AL 3,087,448

THREAD SEVERING Original Filed Feb. 8, 1957 2 Sheets-Sheet 2 United States The present invention relates generally to improvements in lockstitch shoe sewing machines of the McKay type, having rotatably mounted shoe entering horns similar to those disclosed in Uni-ted States letters Patent No. 1,885,- 927 granted November 1, 1932, upon an application of B. T. Leveque, and No. 1,914,936 granted June 20, 1933 on application of F. Ashworth. More particularly, the invention relates to thread trimming devices especially useful in McKay type shoe sewing machines.

The present application is a division of application Serial No. 638,986, led February 8, 1957, now Patent No. 2,979,001, granted April 11, 1961. In addition to the present invention the parent application also discloses a driving and stopping mechanism for causing the shuttle to remain in motion after the needle has stopped in order to set the last stitch of the seam. Also included in the parent application is an improved shuttle driving means now the subject matter of application Serial No. 861,669, tiled December 23, 1959.

In the manufacture of a McKay type shoe a seam is inserted through the ou-tsole, the inturned margin of the upper and the insole. This operation can be performed satisfactorily only by a machine having a shoe entering and supporting horn. At the start of the operation, a length of several inches of thread is withdrawn through the needle threading whirl at the tip of the horn and is held by the operator as the shoe is placed in inverted position upon the horn for the start of the seam. The reason for withdrawing and holding the thread is to prevent the needle from missing the thread on the rst stitch and the whirl from being unthreaded by the subsequent action of the take-up.

The seam in a McKay type shoe is generally inserted about the entire periphery of the shoe, the beginning of the seam being overlapped a few stitches by .the end of the seam. It often happens that the leading end of the needle thread which remains dangling and uncontrolled on the inside of the shoe is picked up at the end of the seam by the needle. The uncontrolled leading end of the thread then tangles with the thread coming directly from the whirl with the result that the needle is often broken, machine adjustments may be disturbed and in some cases the machine may be seriously damaged. Usually the shoe being operated upon is irreparably damaged with a consequent loss of materials and labor.

yIt has long been considered desirable to sever lthe excess thread after the seam has started in order to avoid these odjectionable results. However, in order to cut the thread with a hand held tool it is necessary to interrupt the sewing, raise the presser foot, remove the shoe fro-m the horn, and sever the thread either with an especially formed thread outing instrumentiality or with a conventional knife in a very awkward position. Such a procedure is both time consuming and costly and results in a substantional reduction in production. It is also objectionable because by being forced to handle a sharp instrument frequently in the performance of his duties, the sewing machine operator is exposed .to undue risks of severe lacerations.

The alternative to a hand held tool is a thread severing instrumentality included as a part of the machine. Thread arent 3,087,448 Patented Apr. 30, 1963 yCC cutting devices suitable for severing the needle thread outside Ithe shoe in McKay type shoe sewing machines are disclosed in United States Letters Patents No. 495,-

542 issued April 18, 1893 on an application in the name of V. P. Buck and No. 1,255,489 issued February 5, 1918 on an application in the name of I. Triem. Neither of these devices, however, is readily modifiable for severing the leading end of the needle thread inside the shoe.

It is accordingly an object of the present invention to provide thread severing means in a McKay type shoe sewing machine for severing the leading end of the needle thread inside the shoe after the insertion of the seam has been initiated.

It is another object to provide means for severing the leading end of the needle thread without endangering the operator by exposing him to severe cuts and without increasing the likelihood of damage to the shoe being operated upon.

It is a further object of the invention to provide thread severing means supported upon the horn of a McKay type shoe sewing machine in such a way that it can be readily and quickly removed for replacement or resharpenin Itgis a still further object to provide a thread severing blade which may be readily mounted upon the horn of a McKay type shoe sewing machine Without increasing the size of the drive and whirl enclosing portion of the horn which o-f necessity must enter the shoe. Yet another object is to provide thread severing means mounted upon the horn which is effective only after the insertion of the seam has started so as to prevent displacement of Ithe needle thread in the shoe as the thread is severed. A more general object is to provide a novel and useful method of severing thread.

In the achievement of the foregoing object a feature of the invention resides in the combination of a shoe supporting horn of generally conventional configuration, including a whirl-covering cap with a blade supported on the side of the horn tip in close proximity to the whirl. The blade is formed with an integral tang which enters a slot in the cap. The cutting edge of the blade is positioned in a slight shielding recess near the whirl. The thickness of the blade is controlled with suicient accuracy that it ts snugly between the horn structure and a surface of the cap thereby stiifening the blade and assisting in preventing lateral movement of the cap.

The foregoing objects and features of the present invention will become apparent from the following detailed description taken in connection with the accompanying drawings in which,

FIG. 1 is a view in side elevation of a McKay shoe sewing machine in which the present invention may conveniently be embodied;

FIG. 2`is a detail plan view on an enlarged scale of the tip of the shoe supporting horn including a thread trimming knife according to the present invention;

FIG. 3 is a detail view in perspective of the thread trimming knife included in FIG. 2;

FIG. 4 is a detail view in front elevation and partly in cross section showing the manner in which the thread trimming knife is employed; and

FIG. 5 is a section through the shoe supporting horn illustrating the mounting of the thread trimming knife upon it.

The illustrated machine described in greater detail in the above-identified parent application serves as a setting for the present invention but contains many novel features not necessary `to cooperate with the present thread severing device which may be applied with equal facility to a plurality of McKay shoe sewing machines of either the lockstitch or chain stitch types, including those of the patents already indicated. The present invention will be fully understood from a general description of the associated machine which includes, as shown in FIG. 1, a shoe entering and supporting rotary horn 2 and a sewing head indicated generally at 4. Included in the sewing head are stitch forming devices comprising a straight hook needle S and a shuttle more fully described in the parent application and indicated at 6, for passing loops of needle thread about the locking thread in the formation of the seam. For `feeding the work piece the sewing head includes a feed point 7 actuated by mechanism similar to those described in the above identified patents.

Mounted at the base of the machine is a mo-tor 8 for driving the power actuated parts through a treadle controlled ydriving and stopping mechanism indicated at 9. A main vertical drive shaft 10 is interposed between lthe output of the driving and stopping mechanism 9 and the driven parts located in the sewing head 4 and in the horn 2. A needle threading whirl 12 mounted in the tip of the horn 2 is driven from the main shaft 10 through a series of interconnected shafts 14, 16, 18 and 20. The shaft 20 is journaled in the upper end of the horn, as shown in FIG. 5, and bevel gear teeth formed at its upper end are in mesh with teeth on the whirl for driving the latter to thread the needle in the usual manner of rotary whirls when applied to McKay type shoe sewing machines. It will be appreciated from FIG. 5, that the presence of moving parts in the tip of the horn 2, the size of which must be maintained at a minimum in order to fulfill its required function, presents severe difficulties in the mounting of additional apparatus in close proximity to the whirl.

A modified whirl retaining cap 22 perforated at 23 is secured on the tip of the horn by the screw 24 for confining the whirl and for providing a work engaging upper surface. In some respects the present horn tip portion of the machine is similar to that disclosed in United States Letters Patent No. 1,931,917 granted October 24, 1933, upon application of FredAshworth, but in other respects the addition of a thread severing blade or knife 26 to the horn requires a novel arrangement now to be described.

Both the horn tip proper and the cap 22 have been modified in contour as seen in FIG. 2, to provide a shallow recess 28 into which -the cutting edge of the blade 26 projects. The horn and cap surfaces defining the recess 28 are spaced from the blade 26 a distance slightly greater than the maximum diameter of thread to be employed in the machine and additionally the horn and cap surfaces generally concentric with the axis of the `whirl and intercepted .by an angle a (FIG. 2) serve to guide the vthread into engagement with the cutting edge of the blade.

It will also be appreciated that the enlargement at the tip of the horn shields the sharp edge of the blade 26 so that there is no appreciable danger of injury to the operator when he reaches for the thread at the start of a sewing operation. So `that the thread once guided into engagement with the blade 26 will not escape over the uppermost end of the blade without being severed, the cutting edge is inclined downwardly and slightly away from the axis of the whirl, the inclination being indicated by the angle b in FIG. 4.

In order to secure the blade 26 to the tip of the horn the cap 22 4is formed with .a transverse slot 30 into which is closely fitted an integral attaching tang 32 extending laterally from the body of the blade. In addition to the screw 24 the cap 22 is formed with a single undercut abutment 34 underlying a sloping surface on the horn tip to secure the whirl covering portion of the cap against pivoting upwardly about the screw. To stiffen the blade 26 against lateral bending movement, an intermediate portion of the cap 22 is recessed at 36, the width of the recess `being equal to the thickness of the blade, the upper surface of the blade being substantially coincident with the outer surface of the cap. Since the cap is set in an accurately machined slot in the tip of the horn, the extention of the horn at the blade side toward the whirl reinforces the blade and also prevents lateral looseness Aof the cap.

At the start of a seam a length of thread is withdrawn from the tip of the horn and held in the hand of the operator for ythe insertion of the `first few stitches which secure the thread to the work piece. After two stitches, for example, have been inserted, the iirst stitch hole and hence, the point of exit `of the leading end of the thread from the work piece, has progressed to a point designated by the reference numeral 33 which point is beyond the cutting edge of the blade 26. Since the dangling leading end of the thread has been pulled downwardly against the knife supporting side of the horn, the thread is automatically directed by the guiding surfaces of the horn into a position of engagement with the blade which is hidden from the view of the operator by the shoe itself, in which position it is shown in FIGS. 2 and 4. The operator then applies additional tension to the .thread which is thereby severed. It will be appreciated that although the cutting edge of the blade 26 has been described as located somewhat less than two stitch lengths along the line of the seam away from the axis of the whirl, the invention is not intended to be so limited. It is preferable, however, in order to achieve adequate securement of the thread to the work piece, that two stitches be inserted before the thread severing tension is applied to the thread.

The nature yand `scope of `the invention having been indicated and an exemplary embodiment having been described in detail, what is claimed is:

1. A shoe sewing machine including a rotatably mounted shoe-entering horn formed with a work supporting surface and with a recess close to the surface, work feeding devices, stitch-forming and setting devices, including a straight hook needle, in combination with a thread end trimming knife mounted within the recess and located `below the work supporting surface of the horn, at least one stitch length beyond the needle to sever the thread within a shoe after the first stitch of a seam has been fed by the feeding devices at least one stitch past the needle.

2. A sewing machine having a rotatably mounted shoeentering horn formed with a needle receiving opening at its tip, a straight hook needle alined with the needle receiving opening in the horn, a needle threading Whirl within the opening of the horn, a perforated cap having a work supporting surface and an attached tongue secured to the horn tip to secure the whirl in place and other stitch-forming and setting devices, in combination with an L-shaped thread trimming knife having a sharpened edge at its upper extremity located below the work supporting surface of the cap and formed with a tang on its base adapted to be received in a transverse slot in the cap for the sole securement of the knife between the cap and the horn.

3. A sewing machine having a rotatably mounted shoeentering horn formed with a needle receiving opening at its tip, a straight hook needle alined with the needle receiving opening in the horn, a needle threading whirl within the opening of the horn, a perforated cap having a work supporting surface and an attaching tongue secured to the horn tip to secure the whirl in place and other stitch forming and setting devices, in combination with an L-shaped thread trimming knife located below the Work supporting surface of the cap having a sharpened edge at its upper extremity and forming a tang on its base for securement between the cap and the horn, said cap and horn being formed with a recess into which the sharpened edge of the knife extends and the sewing thread is guided so that it engages the sharpened edge Of the knife as a seam inserted by the machine progresses.

4. An operator controlled sewing machine having a rotatably mounted shoe-entering horn formed with a needle receiving opening at its tip, a straight hook needle alined with the needle receiving opening in the horn, a needle threading whirl within the opening of the horn, a perforated whirl retaining cap having a work supporting surface and secured to the tip of the horn and other stitch-forming and setting devices, in combination with a thread trimming knife having a cutting edge located below the work supporting surface of the cap in close proximity to the whirl, means for securing the knife to the horn, and means on the horn for guiding a portion of the thread hidden from the View of the operator into engagement with the cutting edge of the knife after the beginning of the seam.

5. A sewing machine for inserting stitches in a work piece having a rotatably mounted shoe-entering horn formed with a needle receiving opening at its tip, a straight hook needle alined with the needle receiving opening in the horn, a needle threading Whirl Within the opening of the horn, a perforated whirl retaining cap having a work supporting surface and secured to the tip of the horn and other stitch forming and setting devices, in combination with a thread trimming knife engageable by the thread to be severed beneath the work piece, said knife having a straight cutting edge extending downwardly from the work supporting surface of the cap and away from the axis of .the whirl, and means for securing the knife to the horn.

6. A sewing machine having work feeding devices, a rotatably mounted shoe-entering horn lformed with a needle receiving opening at its tip, a straight hook needle alined With the needle receiving opening in the horn, a needle threading whirl within the opening of the horn, a perforated whirl retaining cap having a Work supporting surface and secured to the tip of the horn and other stitch forming and setting devices, in combination with a thread trimming knife having a straight cutting edge below the Work supporting surface of the cap sloping downwardly and away from the axis of the whirl, means on the horn for directing the thread without interruption in work feed at the beginning of the seam into engagement with the cutting edge of the knife, and means for securing the knife to the horn. Y

References Cited in the file of this patent UNITED STATES PATENTS 463,948 Day Nov. 24, 1891 1,626,329 Cortese Apr. 26, 1927 1,883,746 HDoubler Oct. 18, 1932 1,931,917 Ashworth Oct. 24, 1933 2,476,161 Silverman July 12, 1949 2,558,353 Garcia June 26, 1951 2,651,272 Carter Sept. 8, 1953 

1. A SHOE SEWING MACHINE INCLUDING A ROTATABLY MOUNTED SHOE-ENTERING HORN FORMED WITH A WORK SUPPORTING SURFACE AND WITH A RECESS CLOSE TO THE SURFACE, WORK FEEDING DEVICES, STITCH-FORMING AND SETTING DEVICES, INCLUDING A STRAIGHT HOOK NEEDLE, IN COMBINATION WITH A THREAD END TRIMMING KNIFE MOUNTED WITHIN THE RECESS AND LOCATED BELOW THE WORK SUPPORTING SURFACE OF THE HORN, AT LEAST ONE STITCH LENGTH BEYOND THE NEEDLE TO SEVER THE THREAD WITHIN A SHOE AFTER THE FIRST STITCH OF A SEAM HAS BEEN FED BY THE FEEDING DEVICES AT LEAST ONE STITCH PAST THE NEEDLE. 